DAF 95XF. Manual - part 431

4

XE ENGINE BRAKE

General

95

XF series

2-4

2.4

GENERAL DESCRIPTION OF ENGINE BRAKE SYSTEM

The collective term “engine brake” covers the
exhaust brake or butterfly valve, and the DAF
Engine Brake.

The introduction of the DAF XF 12.6 litre engine
also marks the introduction of a new type of
engine brake for DAF, which is also used on the
XE engines.
This is the DAF Engine Brake, or DEB for short.

Every XE engine has a factory-fitted exhaust
brake.
At customer’s request, the DEB can be installed
at the factory or at a later date.

If the driver activates the engine brake by
means of the engine brake control switch on the
cab floor, both the exhaust brake and the DEB
are engaged. Therefore, the DEB always works
in conjunction with the exhaust brake.

As the CTE-3 checks the activation of the
engine brake, it will disengage the engine brake
below a certain engine speed (see CTE-3
systems manual).

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4

95

XF series

General

XE ENGINE BRAKE

2-5

2.5

DESCRIPTION OF DEB SYSTEM

The DEB consists of two different housings,
each cylinder head having its own DEB housing.
Each housing contains various valves, pistons,
and a magnetic valve.

When the DEB is activated, one exhaust valve
will be opened hydraulically at the end of the
compression stroke. This allows compressed air
to escape to the exhaust system.
The engine now functions as a compressor,
supplying brake power to the vehicle.

Position (A) Induction stroke
The piston moves down and the cylinder is filled
with clean air.

Position (B) Compression stroke
The piston moves up and compresses the air in
the cylinder, creating a reactionary force.
At the end of this stroke, one exhaust valve is
opened briefly. The compressed air can now
escape to the exhaust system.
If the DEB has been activated, no fuel is injected
at the end of the compression stroke and hence
no combustion takes place.

Position (C) Power stroke
The piston moves down and the exhaust valve
closes.

Position (D) Exhaust stroke
The piston moves up, as during a normal
exhaust stroke.

i 400160

i 400165

A

B

C

D

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4

XE ENGINE BRAKE

General

95

XF series

2-6

Operation of the hydraulic DEB

DEB switched off

i 400159

7

6

3

2

10

1

9

4

5

8

A

B

1.

Magnetic valve

2.

Control valve

3.

Operating piston

4.

Main piston

5.

Spring plate

6.

Bridge

7.

Exhaust valve

8.

Exhaust valve rocker

9.

Valve clearance set screw

10. DEB set screw

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4

95

XF series

General

XE ENGINE BRAKE

2-7

Note:
Rockers A and B are not one and the same
rocker (see “Hydraulic control of exhaust
valves”).
A.

Exhaust valve rocker

B.

Exhaust valve rocker

The magnetic valve (1) is not activated.
Lubricating oil cannot pass to the hydraulic
section of the DEB.
In addition, a spring plate (5) ensures that the
main piston (4) remains in the top position.

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